Volt/Ohm Meter

All modern digital meters are capable of many functions. The majority of aircraft avionics/electrical systems troubleshooting is accomplished with four selections.

Most systems use 115 VAC for power applications. Step-down transformers reduce this voltage to 26 VAC for signal voltage and 5 VAC for instrument or panel background lighting.

28 VDC is the standard direct current voltage. 28 VDC is commonly used for relay control, solenoids, and indication lights.

The resistance function is used for continuity certification of wiring. Internal component measurements are also checked with the resistance function.

Proper diode functions are verified with the diode check selection of the VOM.




I usually like to leave a meter in "AUTO" mode for any checks that I am accomplishing. In auto it will indicate correctly no matter what the voltage or resistance might be. If you are using manual, the range must be proper for the system under test. Very often an "OL" is displayed when the meter is not in the correct range.

Having a meter with a backlit display is very helpful. More often than not, you can find yourself jammed in a hole with both hands busy holding test leads. Holding a flashlight in your mouth or having someone else to assist you is not needed.

Diode Check

Resistance

Voltage